1. Chapter 11 Panko and Panko Business Data Networks and Security, 10 th Edition, Global Edition Copyright © 2015 Pearson Education, Ltd. Panko and Panko Business Data Networks and Security, 10 th Edition, Global Edition Copyright © 2015 Pearson Education, Ltd.

2. Chapter (s)CoverageLayers 1–41–4Core concepts and principlesAll 5Single switched networks1–21–2 6–76–7Single wireless networks1–21–2 8 – 10Internets3–43–4 11Applications5 Copyright © 2015 Pearson Education, Ltd. 11-2 Chapter (s)CoverageLayers 1–41–4Core concepts and principlesAll 5Single switched networks1–21–2 6–76–7Single wireless networks1–21–2 8–98–9Internets3–43–4 10Wide Area Networks1-4 11Applications5

3. Basic Networked Application ConceptsE-MailVoice over IPHTTP and HTMLPeer-to-Peer (P2P) Applications Copyright © 2015 Pearson Education, Ltd. 11-3

4.  Application Architectures ◦ How application layer functions are spread among computers to deliver service to users ◦ Stand-alone operation ◦ Client/server operation ◦ Peer-to-peer (P2P) operation Copyright © 2015 Pearson Education, Ltd. 11-4

5. Copyright © 2015 Pearson Education, Ltd. 11-5

6. Copyright © 2015 Pearson Education, Ltd. 11-6

7. Terminal-Host v Client/Server Processing E-Mail Voice over IPHTTP and HTMLPeer-to-Peer (P2P) Applications Copyright © 2015 Pearson Education, Ltd. 11-7

8.  Importance of E-Mail ◦ Universal service on the Internet ◦ Attachments deliver files  Security ◦ A major vector for attacks ◦ Viruses and worms ◦ Spear phishing Copyright © 2015 Pearson Education, Ltd. 11-8

9. Copyright © 2015 Pearson Education, Ltd. 11-9

10. Copyright © 2015 Pearson Education, Ltd. 11-10 When the webpage loads, the user’s “name” is entered into the page’s HTML). However, what appears on the webpage is the script, which the browser executes

11. 2. Simple Mail Transfer Protocol for nearly instantaneous delivery 2. Simple Mail Transfer Protocol for nearly instantaneous delivery 1. Each client PC has its own mail server. 1. Each client PC has its own mail server. Copyright © 2015 Pearson Education, Ltd. 11-11

12. Post Office Protocol or Internet Message Access Protocol, for later receiver downloading Copyright © 2015 Pearson Education, Ltd. 11-12

13. Document standards: RFC 822/2822 for plain text messages. HTML bodies for formatting. UNICODE can represent text in any language. Document standards: RFC 822/2822 for plain text messages. HTML bodies for formatting. UNICODE can represent text in any language. There are separate transmission and document standards. Copyright © 2015 Pearson Education, Ltd. 11-13

14.  Many applications have two types of standards.  Delivery standards ◦ SMTP, POP, IMAP  Message format standards ◦ RFC 822/2822, HTML, UNICODE ◦ It does no good to deliver messages if the receiver cannot understand them. Copyright © 2015 Pearson Education, Ltd. 11-14

15.  Either or both clients can use web-based e-mail instead of SMTP and POP or IMAP.  All interactions for that client take place via HTTP instead.  Message documents are HTML webpages. SMTP HTML HTTP POP/ IMAP Copyright © 2015 Pearson Education, Ltd. 11-15

16. SMTP Process CommandExplanation Receiver220 mail.panko.com Ready When the sending host establishes a TCP session, the receiver signals that it is ready. SenderHELO voyager.shilder.hawa ii.edu Sender indicates that it wishes to communicate. Receiver250 mail.panko.comReceiver signals it is ready to begin message. Copyright © 2015 Pearson Education, Ltd. 11-16

17. SMTP Process CommandExplanation SenderMAIL FROM david@voyager.shidler.hawaii. edu Sender identifies the mail author. Receiver250 OKReceiver signals that will accept a message from this person. Copyright © 2015 Pearson Education, Ltd. 11-17

18. SMTP Process CommandExplanation SenderRCTP TO: ray@panko.com Sender identifies a recipient. Receiver250 OKReceiver will accept mail for this recipient. Copyright © 2015 Pearson Education, Ltd. 11-18

19. SMTP Process CommandExplanation SenderRCTP TO: lee@panko.com Sender identifies a recipient. Receiver550 No such user here Receiver will NOT accept mail for this recipient. Copyright © 2015 Pearson Education, Ltd. 11-19

20. SMTP Process CommandExplanation SenderDATAMessage will follow. Receiver354 Start mail input; end with Permission to send the message body. Copyright © 2015 Pearson Education, Ltd. 11-20

21. SMTP Process CommandExplanation SenderWhen in the course… Sends the body, which ends with a blank line. Receiver250 OKAccepts the body. Copyright © 2015 Pearson Education, Ltd. 11-21

22. SMTP Process CommandExplanation SenderQUITEnding the connection. Receiver221 mail.panko.com Service closing transmission channel Receiver terminates the session. Copyright © 2015 Pearson Education, Ltd. 11-22

23. S: HELO pc-ycc R: 250 euler.im.ncnu.edu.tw Hello …, pleased to meet you S: MAIL FROM: Smith@Alpha.ARPA R: 250 OK S: RCPT TO: Jones@Beta.ARPA R: 250 OK S: RCPT TO: Green@Beta.ARPA R: 550 No such user here S: DATA R: 354 Start mail input; end with. S: Blah blah blah… S: etc. etc. etc. S:. R: 250 OK S: QUIT S: HELO pc-ycc R: 250 euler.im.ncnu.edu.tw Hello …, pleased to meet you S: MAIL FROM: Smith@Alpha.ARPA R: 250 OK S: RCPT TO: Jones@Beta.ARPA R: 250 OK S: RCPT TO: Green@Beta.ARPA R: 550 No such user here S: DATA R: 354 Start mail input; end with. S: Blah blah blah… S: etc. etc. etc. S:. R: 250 OK S: QUIT S: Sender R: Receiver

24.  Viruses, Worms, and Trojan Horses ◦ Widespread problems; often delivered through e- mail attachments  Use of antivirus software is almost universal, but only partially effective, given the number of malware infections.  “Antivirus” programs are not limited to viruses. They scan for many types of malware. Copyright © 2015 Pearson Education, Ltd. 11-24

25. Filtering in two or more locations gives defense in depth. Copyright © 2015 Pearson Education, Ltd. 11-25

26. Copyright © 2015 Pearson Education, Ltd. 11-26 Even if the sender uses SSL/TLS, only the link to its mail host is directly secured.

27. Copyright © 2015 Pearson Education, Ltd. 11-27 SSL/TLS only provides link encryption. Mail servers decrypt and handle before reencrypting if they reencrypt at all

28. Copyright © 2015 Pearson Education, Ltd. 11-28 End-to-end encryption is possible. It is done by the two hosts. However, it is rarely done. It prevents firewall filtering of the message. End-to-end encryption is possible. It is done by the two hosts. However, it is rarely done. It prevents firewall filtering of the message.

29. Terminal-Host v Client/Server ProcessingE-Mail Voice over IP HTTP and HTMLPeer-to-Peer (P2P) Applications Copyright © 2015 Pearson Education, Ltd. 11-29

30.  Transmit voice telephone calls over IP networks  Saves money because the company does not have to maintain separate internal voice and data networks  Saves money because the voice signal is compressed as it is digitized Copyright © 2015 Pearson Education, Ltd. 11-30

31.  Signaling versus Transport ◦ A core concept in telecommunications  Telephony and video ◦ Signaling  Setting up a connection, breaking it down afterward, billing, and so on ◦ Transport  The actual transmission of voice or video Copyright © 2015 Pearson Education, Ltd. 11-31

32. Multimedia PC or VoIP telephone that plugs into an IP network (Internet) Multimedia PC or VoIP telephone that plugs into an IP network (Internet) Copyright © 2015 Pearson Education, Ltd. 11-32

33. Media gateway connects an IP network to the Public Switched Telephone Network. Handles both transport and signaling conversion. Media gateway connects an IP network to the Public Switched Telephone Network. Handles both transport and signaling conversion. Copyright © 2015 Pearson Education, Ltd. 11-33

34. SIP is a signaling protocol. This figures shows connection establishment. SIP is a signaling protocol. This figures shows connection establishment. Copyright © 2015 Pearson Education, Ltd. 11-34

35.  Session Initiation Protocol Signaling Standard ◦ Not just for initiating connections ◦ Opens connections ◦ Closes connections ◦ Handles charges and bookkeeping ◦ In other words, ALL signaling tasks Copyright © 2015 Pearson Education, Ltd. 11-35

36. Transport takes place directly between the caller and called party. Copyright © 2015 Pearson Education, Ltd. 11-36

37.  UDP ◦ There is no time to wait for the transmission of lost packets. ◦ UDP makes more sense because of its lightweight processing and traffic volume requirements.  Real-Time Protocol (RTP) Header ◦ Makes up for two UDP limits. ◦ It adds sequence numbers. ◦ It adds a time stamp for when its codec octets should be played back. Copyright © 2015 Pearson Education, Ltd. 11-37

38.  Codecs translate analog voice to digital transmission signals. Codec Transmission Rate G.71164 kbps (initial telephony standard) G.722 48, 56, 64 kbps G.721 32 kbps G.722.124, 32 kbps G.726 16, 24, 32, 40 kbps G.728 16 kbps G.729AB 8 kbps G.723 5.33, 6.4 kbps G.723.1A5.3, 6.3 kbps In general, greater compression means poorer sound quality. Copyright © 2015 Pearson Education, Ltd. 11-38

39. Terminal-Host v Client/Server ProcessingE-MailVoice over IP HTTP and HTML Peer-to-Peer (P2P) Applications Copyright © 2015 Pearson Education, Ltd. 11-39

40. Again, we see an application with transmission and document standards. Copyright © 2015 Pearson Education, Ltd. 11-40

41. This webpage has text and two graphics. The HTML file has the text and tags for the graphics. Copyright © 2015 Pearson Education, Ltd. 11-41

42. Based on tags in the HTML file, the graphics files are downloaded and rendered on the page. Copyright © 2015 Pearson Education, Ltd. 11-42

43.  Question: How many files will a browser have to download if the webpage has three graphics and plays music when it is downloaded? Copyright © 2015 Pearson Education, Ltd. 11-43